Students: Jessica Brideau*, Michael Harris, Meghan Hutch and Jenna Lynch
Mentor: Suzanne Deschenes
Cadmium and other heavy metals are pollutants known to have toxic effects on marine arthropods. However, horseshoe crabs (Limulus polyphemus) have been known to be extremely resistant to such toxins, for unknown reasons. We carried out this experiment to determine if cadmium exposure of horseshoe crab embryos would lead to molecular damage from reactive oxygen species, or if they would be able to exhibit a defense against this toxin. We performed a 24-hour cadmium exposure on late stage 19 and early stage 20-1 embryos to determine the percentage of dead embryos at increasing concentrations. Through Probit analysis of the resulting dose response curve, the LC25 (5 mg/L) and LC37 (10 mg/L) doses of cadmium were calculated and used in subsequent experiments. To determine whether cadmium induced oxidative damage in the embryos, we performed the thiobarbituric acid reactive substances assay to measure the levels of lipid peroxidation in the form of malondialdehyde (MDA). We found no significant difference in the levels of MDA between cadmium treated and untreated embryos, suggesting that these embryos have defense mechanisms that protect against oxidative damage. There were also no significant differences in mobility between untreated embryos and embryos exposed to 10 mg/L of cadmium. We are currently assessing whether cadmium-treated embryos experienced oxidative DNA damage in the form of 8-oxoguanine and whether increased activity of superoxide dismutase, an antioxidant enzyme, may account for the observed lack of oxidative damage.